These functions maintain numbers stored in base-64 ASCII characters that define a notation by which long integers can be represented by up
to six characters. Each character represents a "digit" in a radix-64 notation.
The characters used to represent "digits" are as follows:
+-----------------------------+-----------------------------+
|Character | Digit |
+-----------------------------+-----------------------------+
|. | 0 |
|/ | 1 |
|0-9 | 2-11 |
|A-Z | 12-37 |
|a-z | 38-63 |
+-----------------------------+-----------------------------+
The a64l() function takes a pointer to a null-terminated base-64 representation and returns a corresponding long value. If the string
pointed to by s contains more than six characters, a64l() uses the first six.
The a64l() function scans the character string from left to right with the least significant digit on the left, decoding each character as
a 6-bit radix-64 number.
The l64a() function takes a long argument and returns a pointer to the corresponding base-64 representation. If the argument is 0, l64a()
returns a pointer to a null string.
The value returned by l64a() is a pointer into a static buffer, the contents of which are overwritten by each call. In the case of multi-
threaded applications, the return value is a pointer to thread specific data.